Process for producing stabilized polyurethane fibers



United States Patent 7 Claims. cl. 260-75) ABSTRACT OF THE DISCLOSURE Stabilized polyurethane fibers are produced by (A) reacting in a solvent which will dissolve polyacrylonitrile (1) an NCO prepolymer prepared from a linear polyester containing terminal hydroxyl groups and an arcmatic diisocyanate with (2) Water and (3) a bifunctional chain extending agent containing tertiary nitrogen compounds and (B) spinning the solution into an elastic fiber having improved dyeability with acidic dyes.

This application is a continuation-in-part of copending application Ser. No. 425,337, filed Jan. 13, 1956.

This invention relates to spandex fibers and to a method of preparing the same. More particularly, it relates to a method of preparing spandex fibers capable of being dyed with acidic dyes.

This copending application discloses and claims a process for preparing spandex fibers by reacting a dihydroxy polyester having an hydroxyl number of 35 to 110 and preferably from 40 to 70 with an excess of from about 115 to about 300% of an aromatic diisocyanate in the melt at a temperature less than 120 C. and then reacting this product with from about 80 to about 120% of water based on the free NCO groups at a temperature of from about to 50 C. and preferably '18 to 40 C. in a polyacrylonitrile solvent. This solution is then degassed and spun into fibers by either the wet or dry spinning method. Such fibers exhibit good textile technological properties such as high tensile strength, low set and a high elasticity modulus. However, they cannot be satisfactorily dyed using anionic (acidic) dyes. Further, dyeing of these spandex fibers in mixtures with other wellknown synthetic fibers cannot be accomplished in the known one-bath procedure.

It has been heretofore known that the dyeability of spandex fibers is improved when basic compositions such as the homopolymerizates of methacrylic acid S-dimethylamino) ethyl esters are added to the spinning solutions. This technique, however, is accomplished by a serious defect in that the storage stability of the spinning solutions in dimethyl formamide and other acrylonitrile solvents is not good because the viscosity of the solution decreases over a period of time. Fibers spun from these solutions have a higher set compared with fibers spun to which basic materials have not been added.

It is thereofe an object of this invention to provide spandex fibers capable of being dyed by acidic dyes. It is also an object of this invention to provide a method of preparing spandex fibers capable of being dyed with acidic dyes. It is still another object of this invention to provide spandex fibers having good textile technological properties which are capable of being dyed by acidic dyes.

The foregoing objects and others which will become apparent from the following description are accomplished 3,376,264 Patented Apr. 2, 1968 in accordance with the invention generally speaking by providing spandex fibers by spinning a polyurethane polymer from a polyacrylionitrile solvent to which has been added a compound having the formula wherein Z is NH or O, T is an alkylene radical having 2 to 8 carbon atoms in the chain, L is Where R is alkyl or cycloalkyl and A is an alkylene or cycloaliphatic radical; and n is 0 or 1. The invention thus contemplates preparing a spinning solution of a polyurethane polymer in a polyacrylonitrile solvent by reacting a dihydric polyester having an hydroxyl number of about 35 to about with an excess of from about to about 300% of an aromatic diisocyana-te based on the hydroxyl groups present, at a temperature of from about 10 to about 50 C. with from about 80% to about based on the free NCO groups remaining of water, this reaction being conducted in a polyacrylonitrile solvent, and during the preparation of the spinning solution, reacting a compound having the formulas set forth above in an amount of from about 1 to about 40% based on the excess of diisocyanate.

In the formulas set forth above, T represents a straight carbon atoms in the chain, for example, ethylene, propylene, butylene, amylene, hexylene, heptylene, octylene, Z-methyl propylene, 2-ethyl propylene, 3-cyclohexyl butylene, 4-propyl butylene, 3-methyl butylene, l-ethyl propylene, 6-cyclopentyl octylene, Z-methyl ethylene and the like; R represents an alkyl or cycloalkyl radical such as, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, n-pentyl and various positional isomers thereof, such as, for example, l-methylbutyl, Z-methylbutyl, 3-methylbutyl, 1,1dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, l-ethylpropyl and the like; corresponding straight and branched chain isomers of hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl and the like; cyclopropyl, cyclobutyl, cycloamyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, cycloundecyl, cyclododecyl, cyclotridecyl, cyclotetradecyl, cyclopentadecyl, cyclohexadecyl, cycloheptadecyl, cyclooctodecyl, cyclonondecyl, cycloeicosyl and the like; A represents an alkylene or cycloaliphatic radical such as, for example, methylene, ethylene, n-propylene, isopropylene, n butylene, isobutylene, sec-butylene, t-butylene, n-pentylene and various positional isomers thereof, such as, for example, l-methylbutylene, 2- methylbutylene, 3-methylbutylene, 1,1-dimethylpropylene, 1,2-dimethylpropylene, 2,2-dimethylpropylene l-ethylpropylene and the like; corresponding straight andbranched chain isomers of hexylene, heptylene, octylene, nonylene, decylene, undecylene, do'decylene, tridecylene, tetradecylene, pentadecylene, hexadecylene, hep-tadecylene, octadecylene and the like; cyclopropylene, cyclobutylene, cycloamyene, cyclohexylene, cycloheptylene, cyclooctylene, cyclononylene, cyclodecylene, cycloundecylene, cyclododcylene, cyclotridecylene, cyclotetradecylene, cyclopentadecylene, cyclohexadecylene, cycloheptadeeylene, cyclooctadecylene, cyclonondecylene, cycloeicosylene and the like.

The compounds having the generic formula set forth are added in an amount based on the excess of diisocyanate present of from about 1 to about 40% and preferably from about 5 to about 30% Specific compounds within the formula represented include N-methyldiethanol amine, N-cyclohexyl-diethanol amine, N('yamino propyl)N,N'-dirnethyl ethylene diamine, N(yamino propyl)N-methyl ethanol amine, N,N'-di(flhydroxy ethyl)N,N-diethyl hexahydro-p-phenylene diamine, N,N-di(' -amino propyl)N,N'-dimethyl ethylene diamine and the like. Preferred, however, are piperazine derivatives such as, for example, N,N'-bis(hydroxyalkyl)- piperazine, N,N"bis(amino alkyl) piperazine, N-(hydroxalkyl)piperazine and N-(amino alkyl) piperazine and particularly, N,N-bis(B-hydroxy ethyl)piperazine, N,N'- bis ('y-amino propyl)piperazine, N-(B-hydroxyethyD-piperazine and N-(fi-amino ethyl) piperazine and the like. The piperazine compounds are preferred because in addition to improving the dye baths of the spun fibers, they also improve the ultraviolet stability of the fibers.

The highly viscous solutions obtained according to the present invention, having a substantially linear molecular structure, do not cross-link on standing even for a long period. In addition, these solutions do not show any degradation phenomena, either at room temperature or at higher temperature, since as a result of their linear molecular structure, no allophanate or biuret groups form in the solvent. After complete degasification in vacuo, they can be spun by the Wet or the dry spinning processes.

Any linear polyesters containing terminal hydroxyl groups, having an hydroxyl number of from about 35 to about 110, preferably from about 40 to about 70 and an acid number below about and preferably between 0 and 3, can be used in accordance with this invention such as, for example, those prepared by reacting a lactone with a suitable initiator such as those disclosed in US. Patents 2,890,208, 2,933,478 and 2,990,379 and those prepared by reacting a dicarboxylic acid with a dihydric alcohol. Any suitable dicarboxylic acid may be used in the preparation of the hydroxyl polyester such as, for example, adipic acid, succinic acid, sebacic acid, suberic acid, oxalic acid, methyl adipic acid, glutaric acid, pimelic acid, azelaic acid, phthalic acid, terephthalic acid, isophthalic acid, thiodipropionic acid, thodibutyric acid, sulfonyl-dibutyric acid, maleic acid, fumaric acid, citraconic acid, itaconic acid and the like. Any suitable dihydric alcohol may be used in the reaction with the dicarboxylic acid to form a polyester such as, for ex ample, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, amylene glycol, hexanediol, hexahydroxylene, glycol, bis(hydroxymethylcyclohexane) and the like. Of course, the hydroxyl polyester may contain urethane groups, urea groups, amide groups, chalkogen groups and the like. Thus, the hydroxyl terminated polyester includes, in addition to hydroxyl terminated polyesters, also hydroxyl terminated polyester amides, polyester urethanes, polyetheresters and the like. Any suitable polyester amide may be used such as, for example, the reaction product of a diamine or an amino alcohol with any of the compositions set forth for preparing polyesters. Any suitable amine may be used such as, for example, ethylene diamine, propylene diamine, tolylene diamine and the like. Any suitable amino alcohol such as, for example, fl-hydroxy ethyl-amine and the like may be used. Any suitable polyester urethane may be used such as, for example, the reaction of any of the above-mentioned polyesters or polyester amides with a deficiency of an organic polyisocyanate to produce a compound having terminal hydroxyl groups. Any of the polyisocyanates set forth hereinafter may be used to prepare such compounds.

Any suitable polyetherester may be used such as, for example, the reaction product of an ether glycol and a polycarboxylic acid such as those mentioned above, with relation to the preparation of polyesters. Any suitable ether glycol may be used such as, for example, diethylene glycol, triethylene glycol, 1,4-phenylene'bis-hydroxy ethyl ether, 2,2-diphenylpropane-4,4-bis-hydroxy ethyl ether and the like. It is desirable to use those polyesters of which the acids and glycols contain a relatively large number of carbon atoms, particularly in order to obtain water-repellent filaments or fibers. It is preferred to use scarcely lengthened and carry free isocyanate groups. It

is obvilously possible, and frequently very desirable, for the proportion of the diisocyanate to be further increased so that free diisocyanate is present in the melt in ad-.

dition to the polyester-diisocyanate adducts. By this increase in the quantity of diisocyanate, it is possible to vary considerably the ratio between soft and hard molecule segments and thus also the elongation at break,

the permanent elongation and the E-modulus of the fila-.

ments and fibers formed in the spinning process.

Any suitable aromatic diisocyanates may be used such as, for example, p-phenylene diisocyanate, 1,5-napthylene diisocyanate, 4,4-diphenylmethane diisocyanate, 3,3

dimethyl-4,4-diphenylmethane diisocyanate, 4,4'-diisocyanatostilbene, 4,4'-diisocyanatodibenzyl and, mixtures of 2,4- and 2,6-toluylene diisocyanate, diphenyl-4,4-diisocyanate and the like. It is. preferred to use symmetrical aromatic diisocyanates and 4,4-diphenylmethane diisocyanate.

The isocyanate-modified polyesters with free isocyanate groups as thus prepared are then dissolved in that quantity of polyacrylonitrile solvent which is necessary for the required final concentration and caused to react at 10 to 50, advantageously at 18 to 40, with to of water, based on the free isocyanate groups which are present. When using water in a quantity less than that necessary for equivalence, the deficiency is notto fall below 20% based on the equivalent quantity.

Any suitable solvent that will dissolve polyacrylonitrile may be used such as, for example, dimethylformamide, dimethylacetamide, dimethylsulphoxide, dimethoxy dimethyl acetamide and the like. They must be free from constituents which are capable of reacting with diisocyanates although they can-contain the usual technical quantity of water and this quantity must then be taken into account as part of the total quantity of water.

When carrying out the reaction, it is not necessary for the isocyanate-modified polyester to be initially dissolved in the quantity of solvent necessary for the required final condensation and then reacted with the water; the isocyanate-modified polyester can be first of all dis-.

solved in a smaller quantity of solvent, whereupon the water necessary for the furtherreaction, possibly already dissolved in more solvent, is added, dilution being effected during the reaction to the required final concentration. According to a preferred embodiment, however, the water in that quantity of solvent which is necessary for the required final concentration is added immediately to the isocyanate-modified polyester. Reaction is allowed to take place for several hours, for example, between 4 and 48 hexamethylene diisocyanate, the reaction products of three mols each of the two aforesaid isocyanates with one mol each of water and one mol of a triol, hexahydrop-phenylene diisocyanate, 4,4-dicyclohexylmethane diisocyanate and 3,3-dimethyl-4,4-dicyclohexylmethane diisocyanate and the like.

It is also possible to add compounds which cause a retardation or acceleration of the polyaddition reactions. With diisocyanates which react particularly quickly, retarding agents, such as acids or acid halides (adiphic acid, hydrochloric acid, benzoyl chloride) can be added in the first phase of the reaction between polyester and diisocyanate. During the later reaction with water, it is frequently desirable to produce acceleration by tertiary amines or heavy metal salts.

The spinnable solutions prepared as described have an excellent stability at room temperature or slightly raised temperature. No break-down of the solutions has been observed, even on relatively long storage. Using the known methods in the spinning art, the solutions are spun to form elastic filaments or fibers, either dry, i.e., at high temperature in air or inert gases, or wet, i.e., high tensile strength, low permanent elongation and high E-modulus. An additional advantage is that the separate capillaries can be easily separated again after coagulation, so that such fibers can readily be used as staple fibers.

In the preparation of the spinning solutions as set forth above, the compounds of the generic formula can be added at any step during the preparation. The compounds can be added to the polyacrylonitrile solutions maintained at to 50 C. and preferably at 10 to C. Subsequently, to this addition, the desired amount of water can be added. It is not absolutely necessary, however, that the isocyanate modified polyester be dissolved in the polyacrylonitrile solvent in the final concentration and then reacted with the basic compound and water. It is also within the scope of the invention to dissolve the modified polyester in a small amount of solvent and then add the basic compound and water which may be dissolved in a further quantity of solvent. This solution can then be diluted during reaction until the desired end concentration is reached. It is preferred that the compound in accordance with the formula set forth and the water are added directly in the total amount to reach the final concentration to the modified polyester. The reaction is permitted to run for several hours, e.g., between 3 and 24 hours at a temperature of 10 to 50 C. and preferably from about 18 to 40 C. Prior to spinning, it is preferred that the solution be degassed under vacuum and that the solids-content of this solution in the time of spinning is from about 10 to about 35%.

In addition to the above defined techniques for adding the. compounds in accordance with the formula set forth, these compounds can also be added within the limits stated to the reaction of the polyester within the aromatic diisocyanate in the melt.

Although the preparation of the spinning solution proceeds faster than in the absence of the compounds in accordance with the formula set forth, the polymers of the fibers formed from the spinning solutions are substantially free of cross-links. These solutions exhibit excellent stability at room temperature or even slightly higher temperatures and do not degrade after long storage periods.

The invention is further illustrated but not limited by the following examples in which parts are by weight unless otherwise specified.

Example 1 About 250 parts of a polyester having an hydroxyl number of 56 and prepared from adipic acid, 1,6-hexanediol and neopentyl glycol in a mol ratio of 10:6.6:3.5 are heated to a temperature of about 75 C. and clear melt results. To this melt, with stirring, is added about 71.9 parts of 4,4-diphenylmethane diisocyanate and maintained at a temperature of about 75 to about C. for about 45 minutes.

(a) The melt of the polyester diisocyanate adduct and free diisocyanate is treated with good stirring with a solution of about 1.25 parts of N,N'-di('y-amino propyl) N,N-dimethyl ethylene diamine and about 2.55 parts of water in about 863 parts of dimethyl formamide at a temperature of about 50 C. After about 5 to 6 hours, the viscosity of the solution is at the desired spinning viscosity. An additional 0.8 part of water is stirred into the solution which is allowed to cool to room temperature. The spinning solution has a solids content of about 27%.

(b) The polyester diisocyanate adduct and free diisocyanate melt is treated while agitated with a solution of about 3.75 parts of N-methyl diethanol amine and about 2.2 parts of water in about 871 parts of dimethyl formamide. The reaction temperature is maintained at about 45 C. After about 6 or 7 hours, the solution has the desired viscosity. An additional 0.7 part of water is added to the spinning solution which is allowed to cool to room temperature. The solids content of the solution is about 27% (c) To the polyester-diisocyanate adduct and free diisocyanate melt is added with agitation, about 1.25 parts of N,N-bis(fi-hydroxyethyl)piperazine and about 2.55 parts of water and about 863 parts of dimethyl formamide at a reaction temperature of about 50 C. After 5 to 6 hours, the solution has the desired spinning viscosity. An additional 0.8 part of water is added to the spinning solution which is allowed to cool to room temperature. The solids content of the solution is about 27%.

(d) To the polyester-diisocyanate adduct and free diisocyanate melt is added, with agitation, 1.25 parts of N,N'-bis(y-amino propyl) piperazine and about 2.6 parts of water in about 908 parts of dimethyl formamide. The reaction temperature is maintained at about 50 C. and after 4 hours, the solution is pigmented with 16 parts of titanium dioxide. After about 4 to 5 hours more, the reaction solution has a very high viscosity. The desired spinning viscosity is reached by dilution with 97 parts of dimethyl formamide and 0.8 part of water. The solids content is approximately 25%.

(e) To the polyester-diisocyanate adduct and free diisocyanate melt is added with intensive agitation about 2.5 parts of N (B-aminoethyhpiperazine and 2.3 parts of water in about 910 parts of dimethyl formamide. The reaction temperature is maintained at about 50 C. and after about 5 hours the solution is pigmented with about 16 parts of titanium dioxide. After about 4 to 5 more hours, the solution has a very high viscosity. It is diluted with 101 parts of dimethyl formamide and 0.8 part of water and permitted to cool to room temperature. The solids content is about 25 Example 2 About 250 parts of the polyester, the composition of which is set forth in Example 1, are melted to a clear melt at about 75 C. To this polyester is added, with stirring, about 78.1 parts of 4,4'-diphenylmethane diisocyanate. The reaction mixture is maintained at a temperature of about 75-80 C. for about 45 minutes. To this reaction mixture are added the quantities of dimethyl formamide, water and N,N-bis(,6-'hydroxy ethyl)piperazine as set forth in Table 1. These quantities result in a solids content of about 27%. The reaction temperature is maintained at about 35 C. After about 10 to about 15 hours, the desired spinning viscosity is reached. Further reaction is stopped by mixing in an amount of water such that the used excess based on the free isocyanate groups in the polyester-diisocyanate reaction melt is about 15 to about 20%. The mixture is then cooled to room temperature.

TABLE 1 from about. 2 to about 10% of dimethyl formamide and 4 I the filaments thus obtained are drawn with a velocity of Addmml r b t 10 t b 50 t t h it b t Dimethyb (fl hydmxy amount of rom a on 0 a out m. mm. 5 rec o rom a u tor amid et Water at Da t 0.5 to about 1.5. The fibers are then dried in an air drier parts gfig 5 and. then stored in containers. These endless filaments are 906 5 0 2 6 0 9 used principally for staple fibers. The textile technological 852 9 properties of the filaments after both dry and wet spinning are summarized in the following Table 3.

TABLE 3 Solution of Spinning Titer in Tensile Elongation, Set,* 300% Example Procedure Denier Strength, Percent Percent Modulus gJden. rug/den.

140 0. 95 600 8 140 30, 000/3, 000 0.53 650 10 100 140 0. 255 550 12 140 140 1.11 000 9 150 140 0. 98 550 s 100 140 1.13 000 s 160 290 1.23 550 12 200 30, 000/3, 000 0. 01 600 14 140 2st) 1. 15 500 14 240 30, 000/3, 000 0. 04 550 14 100 320 0.85 600 s 140 30, 000/3, 000 0. 52 050 s 100 320 0. 78 550 10 100 Set after a triple extension to 300% at a velocity of 150 nun/min. and measured aiter 60 seconds after the last contraction.

Example 3 The fibers thus obtained can be dyed with acidic dyes To about 250 parts of the polyester of Example 1 and the quantities of N,N-bis(l3-hydroxyethyl)piperazine set forth in Table 2 in the molten state at about 75 C. are added under intensive agitation about 71.9 parts of 4,4- diphenylmethane diisocyanate. The reaction is permitted to proceed for about 45 minutes at a temperature of about 75 -80 C. and then the quantities of dimethyl formamide set forth in Table 2 are added. The dimethyl formamide has incorporated therein the quantities of Water also set forth in the table. The quantities of dirnethyl formarnide given are calculated to yield a solids content of 27%. The reaction temperature is maintained at about 50 C. and after about 3-5 hours, the solution has reached the desired spinning viscosity. The reaction is stopped by stirring therein an amount of water calculated to be about 12 to in excess of the free isocyanate present in the polyisocyanate reaction melt. This amount of water is indicated in the last column of the table. The solution is then cooled to room temperature.

Spinning the spinning solutions of Examples 1-3 The elastomeric spinning solutions are degassed in vacuum and filtered. These solutions have the desired spinning viscosity for producing endless multi-fillers, elastomeric fibers having a titer between about 40 and 2000 denier. The solutions are spun through a multi-hole nozzle into a heated channel having substantially no turbulence near the nozzle and which is blown with heated air or inert gas. The solvent containing air is sucked away from the channel ending. The fiber leaving the channel is wound on a spool with a velocity of 200-1000 rn./rnin. The temperature of the channel and the blown air or inert gas is set such that the spun fibers have a final solvent content of less than one percent. To prepare filaments with a titer greater than 5000 and without sticking together of single capillaries of the titer 3 to 30 deniers, the solution is spun through a multi-hole nozzle into an aqueous precipitation bath having a length of from about 10 to 20 meters and maintained at a temperature of from about 20 to about 70 C. The aqueous bath contains alone or in combination with other synthetic filaments capable of being dyed with the same type dyes to produce final products suitable for weaving certain fabrics having stretched properties such as, for example, swimming apparel and the like.

Although the invention has been described in considerable detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for this purpose and that variations can be made by those skilled in the art without departing from the spirit. and scope of the invention except as is set forth in the claims.

What is claimed is:

1. In the process for the preparation of polyurethane fibers which comprises (1) forming a prepolyrner by reacting in the absence of a solvent at a temperature of less than about 120 C. a linear polyester containing terminal hydroxyl groups and having a hydroxyl number of from about 35 to about with an excess from about percent to about 300 percent, based on the polyester hydroxyl groups present, of an aromatic diisocyanate, and (2) reacting said prepolymer with from about 80 percent to about percent of water based on freeNCO groups at a temperature of from about 10 C. to about 50 C. in a solvent which will dissolve polyacrylonitrile, and (3) spinning solution (2) into a fiber, the improvement which comprises, adding to solution (2) fromabout 1 percent to about 40 percent, based on the excess of diisocyanate present, of a compound having the formula:

II-ZT.L (T-Z) H wherein Z is selected from the group consisting of- NHand-O-; T is an alkylene radical having from 2 to 8 carbon atoms in the chain; n is a cardinal number of from 0 to 1; L is a member selected from the group consisting of wherein R is a radical selected from the group consisting of alkyl and cycloalkyl and A is a radical selected from 3. The process of claim 1 wherein the compound rep- References Cited resented by the formula is N,N-bis(hydroxy alky1)piper- UNITED STATES PATENTS azlne.

4. The process of claim 1 wherein the compound repfiifif r sent d by the formula is N,N-bis(amino alkyl)piper- 5 3180853 4/1965 Petrs 5 azine 3 248 370 4/1966 Reischl et a1. 260-75 5. The process of claim 1 wherein the compound represented by the formula is N-hydroxy alkyl piperazine. 3305533 2/1967 Thoma et 260 75 6. The process of claim 1 wherein the compound represented by the formula is N-amino alkyl piperazine. DONALD CZAJA Primary Examme" 10 7. Polyurethane fibers prepared by the process of F. MCKELVEY, AsslstantExammer. claim 1. 

